1. Field of the Invention
The present invention relates generally to a fiber optic receptacle and plug assembly, and more particularly, to a multi-fiber fiber optic receptacle and plug assembly utilizing multiple termination (MT) style ferrules for interconnecting a plurality of optical fibers within a communications network.
2. Technical Background
Optical fiber is increasingly being used for a variety of broadband applications including voice, video and data transmissions. As a result, fiber optic communications networks include a number of interconnection points at which multiple optical fibers are interconnected. Fiber optic networks also include a number of connection terminals, examples of which include, but are not limited to, network access point (NAP) enclosures, aerial closures, below grade closures, pedestals, optical network terminals (ONTs) and network interface devices (NIDs). In certain instances, the connection terminals include connector ports, typically opening through an external wall of the terminal, that are used to establish optical connections between optical fibers terminated from the distribution cable and respective optical fibers of one or more pre-connectorized drop cables, extended distribution cables, tether cables or branch cables, collectively referred to herein as “drop cables.” The connection terminals are used to readily extend fiber optic communications services to a subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH) and “fiber-to-the-premises” (FTTP), referred to generically as “FTTx.”
Conventional connector ports opening through an external wall of a connection terminal include a receptacle for receiving a connectorized optical fiber, such as a pigtail, optically connected within the connection terminal to an optical fiber of the distribution cable, for example in a splice tray or splice protector. At present, these receptacles are relatively large in size because the connection terminal in which they are located does not limit the size of the receptacle. Furthermore, existing receptacles include a receptacle housing defining an internal cavity that houses an alignment sleeve for receiving and aligning the mating ferrules. As previously mentioned, one of the mating ferrules is mounted upon the end of an optical fiber that is optically connected to an optical fiber of the distribution cable within the connection terminal. The other mating ferrule is mounted upon the end of an optical fiber of a drop cable that is inserted into the receptacle from outside the connection terminal. The alignment sleeve of the receptacle assists in gross alignment of the ferrules, and ferrule guide pins or other alignment means assist in more precise alignment of the opposing end faces of the ferrules.
In particular, a fiber optic plug mounted upon the end of a fiber optic drop cable is received within the receptacle through the external wall of the connection terminal. Typically, the plug includes a generally cylindrical plug body and a fiber optic connector including a plug ferrule disposed within the cylindrical plug body. The end of the cylindrical plug body is open, or is provided with openings, so that the ferrule is accessible within the plug body, for example to be cleaned. The plug ferrule is mounted upon one or more optical fibers of the fiber optic drop cable such that mating the plug with the receptacle aligns the optical fibers of the drop cable with respective optical fibers terminated from the distribution cable within the connection terminal. In the process of mating the plug with the receptacle, the plug ferrule is inserted into one end of the alignment sleeve housed within the receptacle. As a result of the construction of a conventional fiber optic plug, the alignment sleeve is minimally received within the open end of the plug body as the plug ferrule is inserted into the alignment sleeve.
Several different types of conventional fiber optic connectors have been developed, examples of which include, but are not limited to, SC, ST, LC, DC, MTP, MT-RJ and SC-DC connectors. The size and shape of the ferrule of each of these conventional connectors are somewhat different. Correspondingly, the size and shape of the alignment sleeve and the plug body are somewhat different. As a result, in conventional practice different fiber optic receptacles and plugs are utilized in conjunction with the different types of fiber optic connectors and/or ferrules. In this regard, the fiber optic receptacles generally define different sized internal cavities corresponding to the size of the alignment sleeve and plug body received therein, and in turn, according to the ferrule of the fiber optic connector to be inserted within the alignment sleeve.
In addition to requiring the use of different fiber optic receptacles and plugs based upon the particular type of optical connectors, conventional receptacle and plug assemblies are typically not compact enough to accommodate high-density installations. Current smaller assemblies, on the other hand, are not able to satisfy the high tensile loads required for FTTx installations, including the 600 lbs. drop cable pull test requirement, and are not able to handle mass interconnections. Exposure to adverse environmental conditions is also a significant issue since current network plans suggest that receptacles may remain unoccupied (i.e., without a mated plug) for an extended period of time. Based on tensile load requirements and the need for prolonged environmental protection, it would be desirable to provide a robust fiber optic receptacle and corresponding fiber optic plug suitable for mounting in a connection terminal or similar enclosure defining an external wall through which optical fibers are interconnected. As yet however, there is an unresolved need for a compact, yet sufficiently robust fiber optic receptacle that is configured to receive only a fiber optic plug having the same type of optical fiber connector as the receptacle. There is a further unresolved need for a fiber optic receptacle and plug assembly adapted to accommodate an alignment sleeve and any type of optical connector, wherein the receptacle and plug define corresponding alignment and keying features. There is an even further unresolved need for a fiber optic receptacle and plug assembly adapted to accommodate multiple termination (MT) style ferrules in opposed relation within a low-profile, environmentally sealed receptacle and plug having improved biasing means and force centering to ensure proper end face to end face physical contact.